1. Field of the Invention
The present invention relates to laminated electronic components in which a resonant line is disposed in a multilayer-circuit substrate to form, e.g., a voltage control oscillator (hereinafter referred to as a "VCO"), and in particular, to a laminated electronic component having a resonant frequency capable of being adjusted by trimming.
2. Description of the Related Art
A multilayer-circuit substrate known as a VCO module, is formed such that an interconnection conductive layer to be provided with electronic components is formed on the top surface, a resonant conductive layer provided with a micro-strip line (hereinafter referred to as an "MSL") as a resonant line is formed in the inside, and a grounded conductive layer for the MSL is formed under the resonant conductive layer or on the base surface. Adjusting the oscillating frequency of the above structured VCO module to a predetermined frequency requires the trimming of the MSL in a production process.
As for a method for adjusting the oscillating frequency, as disclosed in Japanese Patent Unexamined Publication No. 4-329705, there is a conventionally proposed method in which part of an MSL formed in a multilayer-circuit substrate is extracted as an adjustment electrode to the top surface of the multilayer-circuit substrate, and this adjustment electrode is trimmed by appropriate means such as cutting. In addition, as another conventional example, a method for trimming with a laser beam each part of a grounded conductive layer and a dielectric layer and an inside MSL from the base surface of a multilayer-circuit substrate has been proposed.
In the former structure among the above-described conventional examples the part of the MSL needs to be extracted as the adjustment electrode to the top surface of the multilayer-circuit substrate, and the top surface is a mounting surface on which an electronic component is mounted. Thus, the mounting surface must be inevitably expanded, which disadvantageously hinders a reduction in the size of the circuit substrate.
In addition, in the latter structure, a metallic layer to be shrunken when it is trimmed consists of two layers: the MSL and the grounded conductive layer, and the thickness of the dielectric layer from the base surface to the MSL cannot be reduced due to its characteristics. Thus, problems occur in which a laser apparatus with large output is required, which increases costs, and exposure of the MSL after the trimming is performed causes the MSL to oxidize, crack and so forth.